1. Field of the Invention
The present invention relates to radar systems and, more particularly, to Doppler radar systems for tracking targets in high clutter.
2. Related Art
Numerous Doppler radar systems including Doppler processing techniques are available. For example, U.S. Pat. No. 4,137,532 to Taylor, Jr. et al describes a Doppler radar system which has a variable interpulse period (VIP) filter bank to suppress echoes from terrain, rain and chaff. Each filter of the VIP filter bank suppresses a designated frequency band with a width being a large fraction of 1/Tav where Tav is the average period between data samples. The VIP filter bank has seven individual filters. Filter numbers 1 and 7 respond to zero velocity echoes and numbers 2 through 6 provide for echoes having some velocity response. The VIP filter bank is preceded by an MTI canceller that is provided for canceling ground clutter by providing a deep symmetrical notch around zero Doppler frequency.
U.S. Pat. No. 4,622,552 to Andrews et al describes a Doppler processor which has a plurality of (N) transversal filters each of which are delayed by a delay circuit which delays a received signal by a time (T) which equals the interpulse period. The output of the Doppler processor is further filtered by a coherent integration filter to further reduce the level of the clutter components.
However, to date, no suitable method and device of tracking a target in clutter is available which effectively filters clutter from a reflected radar signal.